Vibration absorbers of the prior art are not effectively applicable and adaptable to different vibrating frequencies, require severe power loss, and do not provide a good result. Further, they require auxiliary power consumption, and high manufacturing costs. Moreover, they are applicable only to a limited type of vibrating mass.
Generally, a structure having an internal combustion engine or an electric motor attached thereto has a vibration problem because the structure itself produces an acceleration of vibration. There are various approaches to solve the vibration problem including: reducing the acceleration of vibration itself; reinforcing the structure to withstand the vibration; isolating the structure from the vibration; and the like. However, all such approaches cost excessively, and their applicabilities are very limited.
For example, in a more complex structure such as a large ship having a large engine, the vibration problem can be very serious. A usual approach to solve the problem in such a case is to reinforce the particular portion of the structure, and the rigidity of the engine base. However, such an approach does not provide an effective solution, because, in part, even in the case where the rotational speed of the engine is constant, generating a constant acceleration of vibration, and the problem can be relatively easily solved, an auxiliary system with the characteristic frequency equal to the frequency of an external force has to be attached to the structure for generating an artificial resonance so that a vibration absorber is effectively provided to the structure to reduce a vibration response of the structure.
However, even in this case, the vibration absorbing effect of the vibration absorber can be obtained only at the characteristic frequency of the vibration absorber itself (that is, only when the frequency of the external force corresponds to the characteristic frequency of the vibration absorber). Therefore, such a vibration absorber is not adaptable in cases where the acceleration of vibration is varied as in complex structures such as ships, automobiles, variable electric motors, and the like. Therefore, the vibration problem in complex structures such as ships and the like is solved by installing within the structure a vibration generator, otherwise called vibration balancer, for generating a reverse vibration motive force which offsets a main vibration motive force. But this approach requires a high cost, large space, and high energy consumption for operating a reverse vibration generator.